1. Field of the Invention
The present invention relates generally to a color television signal transmitting system and more particularly relates to an apparatus for recording and reproducing a video signal on a recording medium by frequency modulation and demodulation.
2. Description of the Prior Art
In the existing broadcasting video tape recorder (VTR), a carrier wave is directly FM (frequency modulation) modulated by a composite video signal, this FM-modulated video signal is recorded on a magnetic tape, the recorded video signal is reproduced therefrom and then demodulated, whereby a reproduced picture of high quality is obtained.
However, in the above direct FM-modulation system, the frequency of the FM carrier wave is close to the frequency band of the video signal so that particularly when recording and reproducing a composite color television signal that has a color subcarrier wave in a relatively high frequency band of the video signal frequency, there is an essential problem such as moire, over-modulation, deterioration of DP (differential phase) and DG (differential gain) characteristics and so on. Further, since color information is contained in the phase of the color subcarrier wave, irregularity of color is caused by jitter of a video tape recorder (VTR). In this case, a fast jitter component can not sufficiently be removed even by using a time base corrector.
To overcome the above shortcomings of the direct FM-modulation recording system of the composite color video signal, a technique in which a video signal is transmitted in the form of a component signal is disclosed in, for example, a document of a Japanese patent application examined No. 13538/1969. Although the composite video signal can be transmitted via one transmission system, strict requirements for S/N (signal-to-noise) ratio, phase characteristic, jitter of the transmission system and so on are not completely satisfied. As a result, in the invention disclosed in the above document, a chromaticity signal derived from a parallel color signal formed of a luminance signal and at least two chromaticity signals is time-compressed so as to make its frequency band substantially the same as that of the luminance signal. This time-compressed chromaticity signal is inserted into a horizontal blanking period of the luminance signal or the nearby portion thereof, to thereby provide a serial color signal and then this serial color signal is transmitted.
When the component video signal is directly obtained from a video camera, it is possible to transmit the video signal with high quality by using the above technique. However, most of the existing broadcasting video camera is adapted to produce the composite video signal so that in order to obtain the above time-compressed serial color signal, it is unavoidable to carry out a separation of the luminance signal Y and the chromaticity signal C (hereinafter simply referred to as Y/C separation).
However, in the prior art Y/C separation of an analog signal, the quality of the separated signals is considerably deteriorated so that the afore-noted high quality signal transmission technique can not be employed.